1. Field of the Invention
The present invention relates to a video processing apparatus that can display a captured image together with a mask image superimposed at a mask area thereof, and further relates to an imaging apparatus, a video processing method, and a storage medium.
2. Description of the Related Art
There is a conventionally known masking technique capable of superimposing a mask image on a partial area of an image captured by an imaging apparatus to prevent a specific image portion on which the mask image is superimposed from being viewed.
In general, an image capturing area (hereinafter, referred to as “imaging area”) of an imaging apparatus can be expressed as an area in spherical coordinates illustrated in FIG. 8A, in which the imaging apparatus is positioned at the center thereof, when the imaging apparatus faces a predetermined direction. Further, FIG. 8B illustrates a projected image obtainable when a captured image of the imaging area in the spherical coordinates is projected on a flat plane. As understood from FIG. 8B, an image portion positioned in a peripheral region of the captured image is greatly distorted when it is projected on the flat plane, compared to an image portion positioned at the center of the captured image.
In such an imaging apparatus, if superimposition of a mask image is performed using the above-described masking technique, an area to be covered by the mask (hereinafter, referred to as “mask area”) having been set in the spherical coordinates may become a distorted area on a flat plane. For example, when a mask area “abcd” is set as a mask setting area as illustrated in FIG. 8A, if the mask area “abcd” is projected on a plane, the area “abcd” becomes a distorted area as understood from FIG. 8B.
Hence, as discussed in Japanese Patent Application Laid-Open No. 2001-069494, a conventional imaging apparatus is arranged to adjust an imaging direction thereof in such a way as to bring the center of the imaging area into coincidence with the center of a mask area to be set. Therefore, it becomes feasible to perform mask area setting at a central region of a screen.
However, in a case where the imaging direction of the imaging apparatus is fixed, it is unfeasible to adjust the imaging direction for the mask area setting. Accordingly, a mask area having been set in the spherical coordinates may become a distorted area when it is projected on a flat plane. Further, even in a case where the imaging direction is changeable, a significant amount of time and labor will be required if the direction of a camera is changed each time when the mask area setting is performed.